The subject matter of this disclosure, in one implementation, relates to an isolator circuit for providing current and/or voltage isolation inside an integrated circuit (“IC”) package. Isolator circuits are used to couple signals between circuits having different ground reference potentials, and to provide ground reference potential isolation inside IC packages. In some applications, different grounds inside IC packages can have a difference in potential as high as several thousand volts.
Generally, there are three methods for providing isolation between circuits having different ground reference potentials: opto-coupled isolation, transformer-coupled isolation, and capacitively-coupled isolation. Opto-coupled isolation and transformer-coupled isolation are generally disadvantaged in that the coupling devices are relatively bulky and not well suited for use inside an IC package. Capacitors, on the other hand, can be made smaller and be integrated on a semiconductor die.
However, attempts in the past to provide an isolator circuit on a single semiconductor die have been met with problems due to reliability constraints and damage from electrostatic discharging and over voltage breakdown. In particular, it has been found to be difficult to provide silicon dioxide-based suspended isolating interconnects capable of withstanding the high voltage differential commonly encountered in isolator circuits. Similarly, it has been found to be difficult to increase the voltage on a single semiconductor die to extremely high working voltages (e.g., 2000 volts).